Your DVDRs say 120 minutes because the manufacturers want to appeal to customers who don't understand what gigabytes are. Your '120 minute' DVDR is really a 4.7 gigabyte DVDR. If you really want to know, a 4.7 gigabyte DVDR won't even hold 4.7 gigabytes. It's more like 4.4 gigabytes.

So...it doesn't matter how 'long' your movie is. Movies encoded at a high bitrate (high quality) take up more space than those encoded at lower bitrates.

In conclusion, if it's less than 4.4 gigs then it will fit. If it's more then it won't fit.

Hope this helps

Dano